Burst read addressing in a non-volatile memory device

Abstract

A synchronous flash memory has been described that includes an array of non-volatile memory cells. The memory device has a package configuration that is compatible with an SDRAM. The synchronous flash memory device includes an array of non-volatile memory cells arranged in a plurality of rows and columns. During a read operation, a row of the memory array can be accessed and data read from a group of columns during a burst operation. The burst columns are generated using an internal counter and an externally provided start address. The memory generates the burst column addresses by modifying the least significant column address signals only. For a burst length of two, only the least significant address bit is modified. For a burst length of four, only the two least significant address bits are modified. Finally, only the three least significant address bits are modified for a burst length of two. In one embodiment, the burst addresses rotate through the defined column group in a cyclical manner.

1. A synchronous flash memory device comprising:
 an array of non-volatile memory cells arranged in addressable rows and columns; 
 a plurality of address inputs, coupled to the array of non-volatile memory cells, comprising at least A 2 , A 1 , and A 0 ; and 
 a state machine that can execute a method for reading a synchronous flash memory device including receiving an initial column address on address inputs A 2 , A 1 , and A 0 , initiating a burst read operation in response to the burst mode command and the burst length, and, using an internal counter circuit, generating additional column addresses starting at the initial column address, wherein the internal counter changes a signal only on column address input A 0  if the burst length is two, the internal counter changes signals only on column address inputs A 0  and A 1  if the burst length is four, and the internal counter changes signals only on column address inputs A 0 , A 1  and A 2  if the burst length is eight. 
 
     
     
       2. The device of  claim 1  and further including a mode register that contains a mode of operation of the memory device. 
     
     
       3. The device of  claim 2  wherein the mode register contains the burst length and a burst type. 
     
     
       4. The device of  claim 2  wherein the mode register is comprised of a non-volatile register and a volatile register. 
     
     
       5. The device of  claim 4  wherein contents of the non-volatile register are loaded into the volatile register during an initialization operation. 
     
     
       6. A synchronous flash memory device comprising:
 an array of non-volatile memory cells arranged in addressable rows and columns; 
 a plurality of address inputs, coupled to the array of non-volatile memory cells, comprising at least A 2 , A 1 , and A 0 ; and 
 a state machine that can execute a method for reading a non-volatile synchronous memory device including receiving an initial column address on address inputs A 2 , A 1 , and A 0 , initiating a burst read operation in response to the burst mode command and the burst length, and, using an internal counter circuit, generating additional column addresses starting at the initial column address, wherein the internal counter changes a signal only on column address input A 0  if the burst length is two, the internal counter changes signals only on column address inputs A 0  and A 1  if the burst length is four, and the internal counter changes signals only on column address inputs A 0 , A 1  and A 2  if the burst length is eight such that when the internal counter reaches the burst length, it counts from the initial column address in a cyclical manner and when the internal counter reaches a maximum column address for a particular burst length, it counts up cyclically from 0. 
 
     
     
       7. The memory device of  claim 6  wherein the burst length determines a maximum quantity of column addresses that can be accessed during a read command. 
     
     
       8. The memory device of  claim 6  and further including a mode register wherein bits M 0 –M 2  specify the burst length and bit M 3  specifies a burst type. 
     
     
       9. The memory device of  claim 8  wherein the burst type comprises one of sequential or interleaved. 
     
     
       10. The memory device of  claim 6  and further comprising command execution logic, coupled to the state machine, for receiving and interpreting commands to the memory device. 
     
     
       11. The memory device of  claim 10  wherein the command execution logic comprises a mode register. 
     
     
       12. The memory device of  claim 10  wherein the command execution logic comprises a non-volatile mode register and a volatile mode register wherein contents of the non-volatile mode register are loaded into the volatile mode register during an initialization operation. 
     
     
       13. The memory device of  claim 6  wherein the state machine is further able to execute a read command in order to initiate the burst read operation. 
     
     
       14. An electronic system comprising:
 a processor for generating a read command and a burst length; and 
 a synchronous flash memory device coupled to the processor, the device comprising:
 an array of non-volatile memory cells arranged in addressable rows and columns; 
 a plurality of address inputs, coupled to the array of non-volatile memory cells, comprising at least A 2 , A 1 , and A 0 ; and 
 a state machine that can execute a method for reading a non-volatile synchronous memory device including receiving an initial column address on address inputs A 2 , A 1 , and A 0 , initiating a burst read operation in response to the read command and the burst length, and, using an internal counter circuit, generating additional column addresses starting at the initial column address, wherein the internal counter changes a signal only on column address input A 0  if the burst length is two, the internal counter changes signals only on column address inputs A 0  and A 1  if the burst length is four, and the internal counter changes signals only on column address inputs A 0 , A 1  and A 2  if the burst length is eight. 
 
 
     
     
       15. The system of  claim 14  and further including command execution logic coupled between the processor and state machine for interpreting the read command and storing the burst length in a volatile register. 
     
     
       16. The system of  claim 15  wherein the processor further generates a burst type that is stored in the register. 
     
     
       17. The system of  claim 16  wherein the burst type is one of interleaved or sequential. 
     
     
       18. The system of  claim 15  wherein the command execution logic comprises a non-volatile register for storing data upon power-down of the device. 
     
     
       19. The system of  claim 18  wherein the command execution logic is capable of loading the data from the non-volatile register to the volatile register on power-up.